This invention relates to an apparatus for assisting in maintenance of rail roadbeds. More specifically, it relates to an apparatus for guiding new ties into the roadbed and for holding tie plates against rails when ties are being replaced.
In order to maintain railroad tracks in safe operating condition, it is necessary to replace the ties periodically. The ties (made of wood, metal or concrete) underneath the rails tend to wear out after an extended period of use. Various machines have been developed for removing and/or inserting the ties.
Among problems encountered in use of such machines are the handling of the tie plates when old ties are removed. Manual handling of the tie plates slows down the process and increases costs and safety risks. Absent intervention, the tie plates simply drop to the roadbed when the old ties are removed.
Another problem is getting a new tie to slide into the cavity left by removal of the old tie without catching on the rails (which rails are lifted during removal and insertion), any tie plates held against the rails, and other obstructions.
The following U.S. patents, assigned to the assignee of the present application and hereby incorporated by reference, show various such machines:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 4,951,573 Madison August 28, 1990 5,048,424 Madison et al September 17, 1991 5,197,389 Glomski et al March 30, 1993 ______________________________________
Madison '573 discloses a tie remover/inserter using the structure of a modified backhoe.
Madison and Newman '424 discloses a tie replacer including a tie guide structure to help guide the new tie into proper position without catching on obstructions. It uses electromagnets to hold tie plates against the uplifted rails.
Glomski, Newman, and Madison '389 discloses a tie replacer with a tie guide assembly and air-cylinder operated magnets to hold the tie plates against the rails.
U.S. Pat. No. 4,241,663 issued Dec. 30, 1980 to Lund et al. discloses use of electromagnets to hold tie plates to rails.
Although those and various other devices for tie plate handling and/or tie guiding have been generally useful, they have been subject to one or more disadvantages.
Those devices using magnets or electromagnets for holding tie plates often pick up metal parts (such as loose tie plate spikes) other than tie plates. Such other metal parts may prevent the devices from securely holding the tie plates against the rails. Further, even non-metallic debris, such as ballast, may get between the tie plates and the magnets or electromagnets and cause tie plates to drop free of the rails.
The guide assemblies or structures for guiding ties into place often still have problems with debris blocking ties as they go into place. Further, it often requires great force to overcome friction and to get the ties into place using such tie guides. Finally, such tie guides often allow or cause wandering of the tie as it is inserted. In other words, the tie doesn't maintain its orientation perpendicular to the rails during insertion.